Ordinary machine vises provided to hold and support pieces of work in predetermined position in related machine tools include elongate beds with front and rear ends and longitudinally extending rails, fixed or stationary jaws with flat vertical rearwardly disposed faces projecting upwardly from the front ends of the beds, upwardly projecting movable jaws with forwardly disposed faces rearward of the fixed jaws and having guideways engaged with the rails; and manually operable screw means carried by the beds, rearward of and engaging the movable jaws to move them longitudinally toward and away from the fixed jaws, as desired or as circumstances require.
Further, in practice, ordinary machine vises of the character referred to are provided with removable and/or replaceable jaw plates. The jaw plates are arranged in flat bearing engagement on the faces of the vise jaws and are releasably secured thereto by screw fasteners.
Machine vises of the character referred to above are widely used throughout the art of machining and are well-known to those familiar with the art to which my invention relates.
In the course of using vises of the character referred to above, the beds of the vises are arranged and supported on work tables or the like of related machine tools and items of work to be worked upon are manually arranged in desired predetermined relationship relative to the stationary jaws and the movable jaws are advanced into engagement with the items by work, by manually operating the screw means of the vises.
The above procedure of arranging and clamping an item in a vise must, as a general rule, be carried out with great care and skill since the item of work must be supported by the vise in precise, predetermined position within the working area of its related machine tool, before it is worked upon. As a result of the foregoing, the noted procedure is time-consuming and therefore extremely costly.
In practice, where a plurality of items or pieces of work are to be worked upon in and by a machine tool, the machine vise is mounted on the work table of the tool with its stationary jaw in fixed predetermined position and so that when the work pieces are arranged between the jaws, the machinist need only manually adjust the position of the work laterally and vertically relative to the fixed jaw, preparatory to advancing the movable jaw into clamped engagement with it. This modified procedure often materially reduces set up time, that is, the time required to effect positioning and clamping of a piece of work within the vise and relative to the machine tool.
When a large number of like pieces of work are to be worked upon and to further reduce the set up time, skilled machinists frequently make and arrange "steady rest" blocks and the like on the beds of the vises, between the jaws thereof, to stop and support the pieces of work in predetermined vertical position between the vise jaws, whereby they need only concern themselves with lateral positioning of the work pieces, when setting up the work.
While the last noted modified procedure and use of separate steady rest means is effective to further reduce set up time, it is only practiced when the number of pieces of work to be worked upon is sufficient to justify the time and expense that is required to make a suitable steady rest structure and/or means.
As a general rule, when the number of pieces of work is sufficient to justify the making of special steady rest means for use within machine vises, the time and expense in producing full production tooling is generally warranted and the use of a conventional machine vise is dispensed with.
Prior to the present invention, the only teaching in the prior art which provides economically feasible and practical means to simplify and reduce the time required to set up a limited number of pieces of work in a machine vise is disclosed in U.S. Pat. No. 4,216,950, issued Aug. 12, 1980, and entitled "STEADY REST". That patent discloses a common machine vise with jaw plates fixed to the vise jaws. The jaw plates carry elongate vertically shiftable bar-like work piece engaging steady rests. The steady rests have guide blocks projecting into openings in the jaw plates and are carried by vertical screws rotatably carried by the plates and extending through the blocks. Upon rotation of the screws in the plates, the steady rest bars are raised and lowered, as desired. While the foregoing structure is effective and has great utility when close tolerances need not be maintained, it is seriously deficient and of limited utility when close tolerances must be maintained. This is due to the fact that the stability afforded by the screw thread connection between the screws and steady rest bars is inherently sloppy and is such that the bars tend to rock or teeter-totter relative to the screws when minor vertical loads are applied to the end portions of the bars. Efforts to eliminate the noted shortcoming in the above noted steady rest means, by providing close tolerances in the threads has resulted in threads which cannot be effectively turned, before acceptable stability of the steady rests is achieved.
As a result of the foregoing, the practical use to which the noted patented steady rest can be put is limited.